Gyratory crushers are used for crushing ore, mineral and rock material to smaller sizes. Typically, the crusher comprises a crushing head mounted upon an elongate main shaft. A first crushing shell (typically referred to as a mantle) is mounted on the crushing head and a second crushing shell (typically referred to as a concave) is mounted on a frame such that the first and second crushing shells define together a crushing chamber through which the material to be crushed is passed. A driving device positioned at a lower region of the main shaft is configured to rotate an eccentric assembly positioned about the shaft to cause the crushing head to perform a gyratory pendulum movement and crush the material introduced in the crushing chamber. Example gyratory crushers are described in WO 2004/110626; WO 2008/140375, WO 2010/123431, US 2009/0008489, GB 1570015, U.S. Pat. No. 6,536,693, JP 2004-136252, U.S. Pat. No. 1,791,584 and WO 2012/005651.
Primary crushers are heavy-duty machines designed to process large material sizes of the order of one meter. Secondary and tertiary crushers are however intended to process relatively smaller feed materials typically of a size less than fifty centimeters. Cone crushers represent a sub-category of gyratory crushers and may be utilised as downstream crushers.
Typically, both the inner and outer crushing shells wear and distort due to the significant pressures and impact loading forces they transmit. In particular, it is common to use backing compounds to structurally reinforce the outer shell and assist with contact between the radially outward facing surface of the outer shell and the radially inward facing surface of the topshell. In particular, a backing compound (typically an epoxy or polyurethane material) is cured around the outer region of the concave to provide structural support to the concave during the crushing operation particularly in tough high-pressures applications involving, for example, processing extremely hard materials. Example backing compounds are available from ITW (‘Korroflex’) Ltd, Birkshaw UK under brand names Korrobond 65™ and 90™; and Monach Industrial Products (I) Pvt., Ltd, India, under brand name KrushMore™.
However, the majority of widely used backing compounds are disadvantageous for health and environmental reasons and require long curing times that extend the downtime of the crusher. Accordingly, there is a general preference to avoid their use. However, the backing material also has a further function to seal the region between the outer crushing shell and the topshell (or intermediate spacer ring) to prevent downward passage of debris particles and dust into the region between the crushing shell and the topshell which is undesirable. Accordingly, there is a need for an outer crushing shell configured for use without a backing compound whilst facilitating a means of sealing the radially outer region between the crushing shell and the topshell (or intermediate spacer ring) to prevent the ingress of contaminant particles and fines.